For many years, both direct current (DC) and alternating current (AC) power lines have been used in order to transfer data from one device to another. Recently, there has been a growing need for new data transmission services and applications that are more reliable and support higher data rates over these power lines. For instance, remote metering, smart grids, industrial and home automation are merely some of the upcoming applications that are currently using power lines to support data communications and greater use of these power lines is expected.
One primary disadvantage in using power lines for data transfer is that power lines are hostile environments. In fact, communication channels supported by these AC power lines tend to experience severe non-linear behavior. In particular, channel characteristics and parameters may vary due to changes in frequency, location, time and even the type of equipment deployed. As an example, the impedance of a power line may appear to be 1-2 ohms (Ω), but as the frequency of signaling applied to the power line increases, the impedance of the power line also increases. This increased impedance causes increased signal noise that may hamper proper detection of the data at an intended destination.
FIG. 1 illustrates an exemplary noise power distribution 100 with frequency bands 110-112 supported by European (CELENEC), United States (FCC) and Japan (ARIB) power line standards respectively, as outlined in Table A.
TABLE ALOWHIGHFREQFREQSTANDARDS(KHz)(KHz)FCC10480ARIB10450CELENEC A995CELENEC B95125CELENEC C125140CELENEC B, C95140
As illustrated in FIG. 1, a low frequency region from three kilohertz (3 kHz) to 500 kHz is especially susceptible to interference such as narrowband interference and/or intersymbol interference (ISI), which may occur if orthogonal frequency division multiplexing (OFDM) is used as the selected data transmission scheme.